1. Field of the Invention
The present invention relates generally to a leveling apparatus for excavator and forestry machine equipment, and more particularly to an improved leveling apparatus for excavator and forestry machine equipment, which is mounted between an upper swing structure and a lower driving structure to control a tilt level of the upper swing structure, which is varied depending on the ruggedness of ground or mountainous areas, without any interference with an upper frame or a track chassis.
2. Description of the Prior Art
Conventionally, heavy equipment, such as an excavator, a harvester for logging operations, and the like, may include a working device selectively mounted on an end part of a boom and having headers for logging operations, such as a bucket, a hydraulic saw, and an electric saw, in accordance with working requirements. Since the heavy equipment performs the work as it moves on the inclined ground, the equipment may be tilted to one side or may overturn due to the inclination of the ground.
For example, in the case where the heavy equipment performs a work or moves on the inclined ground, such as a slope, a hill, and the like, against a horizontal surface H, the tilt of the equipment is changed. Here, the tilt of the equipment means a range in which the equipment, the upper swing structure, or the lower driving structure is tilted to a forward, backward, or side direction against the horizontal surface H. If the tilt of the equipment is severely changed, the center of gravity of the equipment may move to an outside of a track of the lower driving structure to cause overturning of the equipment.
In particular, the heavy equipment, such as an excavator, a tree harvester for logging operations, and the like, keenly requires a leveling apparatus for moving the lower driving structure to the forward, backward, or side direction, or for smoothly performing a tilt operation at a specified angle when the tilt of the equipment is changed due to the inclination of the ground E.
According to a conventional leveling apparatus for excavator and forestry machine equipment, a geared mechanism for simply moving the center of gravity of the upper swing structure in every direction using a pinion-rack gear and a guide rail has been known. However, this technique has a drawback in that it cannot change the tilt angle of the upper swing structure.
In order to solve the above-described problem, a tilt mechanism for controlling the tilt of the equipment through tilting of the upper swing structure in every direction as supporting the load of the upper swing structure using a driving force of the actuators and a tilt shaft has been known in the art.
For example, U.S. Pat. No. 6,609,581 assigned to Tigercat Industries Inc. discloses a tilt mechanism using two actuators. According to the technology disclosed therein, two actuators are fixed to an inside of track chassis, and an upper swing structure is tilted around one tilt shaft on a lower frame provided in the lower driving structure to keep the leveling of equipment. However, this technology has the drawback in that a great load is applied to the actuators in accordance with the tilt of the equipment and the structure of the tilt mechanism and the lower frame is complicated.
As another tilt mechanism for leveling heavy equipment, U.S. Pat. No. 6,173,973 assigned to Timberjack Inc. discloses a tilt mechanism using four actuators. According to this technology, one tilt shaft is provided on a frame of a lower driving structure, and plural actuators are link-coupled to the tilt shaft and a turntable to tilt the upper swing structure in every direction.
According to this technology, however, since the actuators are arranged to be inclined inside the lower frame and the tilt is performed along with a journal shaft and a link structure, the tilt range of the upper swing structure may lean upon an inclined ground surface in the forward/backward direction or an inclined ground surface in the left/right direction of the equipment, and this makes the control of load required in the actuators difficult. Also, the capacity and the size of the actuators become unbalanced and the whole height of the heavy equipment is increased.